A power brake is a machine utilized for bending sheet metal. Commonly, a power brake includes a ram member carrying a male die part, the latter being movable toward and away from a female die part mounted on a fixed bed. Typically, the female die part defines an upwardly open channel. When the machine is used to make a bend in a piece of sheet metal, the portion of the sheet metal in front of the die swings upward very quickly, this movement being referred to in the trade as a "whip".
It is desirable to provide some means for ensuring that the operator of a machine of this type will not, through inadvertence or mistake, insert a finger or hand between the die parts just as the ram member is descending.
Several different methods have been used to accomplish this safety feature in the past. For example, it is known to provide a machinery operator with wrist bands that are attached to cables connected behind or above the operator at some fixed point. The cables are of such a length that they prevent the operator from moving his hands into the machinery. The primary disadvantage of guard of this type is that many workers simply will not wear them.
It is also known to provide a guard in the form of two switches that must be simultaneously depressed by both hands of the operator before the machine will operate. This guard system, although satisfactory, cannot be used with a piece of machinery which requires the operator to hold the workpiece in position while it is being operated upon by the machine. This is often the case with a brake press. For example, where a brake press is being used to fold sheet metal into a box, the operator must hold the sheet metal during the bending operation or it will simply fall out of the machine.
It is known to provide a safety guard in the form of a downwardly depending and vertically movable sheet of plastic or the like, positioned normally to partly block the opening through which sheet metal is fed to a brake press, as disclosed for example in U.S. Pat. No. 3,186,256, L. Reznick, issued June 1, 1965 and entitled "Safety Guards for Brakes, Punch Presses and Similar Machines".
A typical disadvantage of prior art safety guards suspended from the machine itself, however, is that there has been no provision for preventing the operator from simply taking hold of the safety guard and raising it or pulling it out of the way prior to operation of the machine to bend the sheet metal. Hence, such prior art safety guards do not constitute a positive deterrent preventing the operator from mangling his hands and fingers.
Accordingly, it is an aspect of this invention to provide a safety guard for brake presses and similar machines, which is positively retained in the "guard" position until the machine is operated, and which upon operation of the machine is automatically raised upwardly to allow for the "whip" movement of the projecting portion of the sheet metal.